In CATV networks, there are cases wherein a transmission route needs to be modified due to an increase in the number of subscribers or relocation of a relay station or the like.
If the number of subscribers increases, the number of branches (distributions) must be increased. If a relay station or the like is relocated, there may be cases wherein the direction of transmission becomes opposite.
With conventional directional couplers, such cases must be coped with by replacing a tap plate with one for an increased number of branches. To reverse the direction of transmission, the cable connections are reversed, or the direction coupler itself is remounted in a reversed right-left position.
However, the reversing of cable connection may not be easy. If an existing cable may be disconnected, the cable may well be too short to connect to the opposite terminal. Since an extension cable cannot be used for the reconnection, it becomes necessary to replace all the cables along the route to be modified. The costs required therefor is unignorable.
The remounting of a direction coupler into a reversed right-left position is not easy, either. Since cables used for CATV are thick and difficult to handle, it is not easy to disconnect cables from and reconnect the cables to a direction coupler.
In works for reversing the direction of transmission, increases in the number of branches are often required as well.